TOI-2084 b and TOI-4184 b: Two new sub-Neptunes around M dwarf stars

Barkaoui, K.; Timmermans, M.; Soubkiou, A.; Rackham, B. V.; Burgasser, A. J.; Chouqar, J.; Pozuelos, F. J.; Collins, K. A.; Howell, S. B.; Simcoe, R.; Melis, C.; Stassun, K. G.; Tregloan-Reed, J.; Cointepas, M.; Gillon, M.; Bonfils, X.; Furlan, E.; Gnilka, C. L.; Almenara, J. M.; Alonso, R.; Benkhaldoun, Z.; Bonavita, M.; Bouchy, F.; Burdanov, A.; Chinchilla, P.; Davoudi, F.; Delrez, L.; Demangeon, O.; Dominik, M.; Demory, B.-O.; de Wit, J.; Dransfield, G.; Ducrot, E.; Fukui, A.; Hinse, T. C.; Hooton, M. J.; Jehin, E.; Jenkins, J. M.; Jørgensen, U. G.; Latham, D. W.; Garcia, L.; Carrazco-Gaxiola, S.; Ghachoui, M.; Gómez Maqueo Chew, Y.; Günther, M. N.; McCormac, J.; Murgas, F.; Murray, C. A.; Narita, N.; Niraula, P.; Pedersen, P. P.; Queloz, D.; Rebolo-López, R.; Ricker, G.; Sabin, L.; Sajadian, S.; Schanche, N.; Schwarz, R. P.; Seager, S.; Sebastian, D.; Sefako, R.; Sohy, S.; Southworth, J.; Srdoc, G.; Thompson, S. J.; Triaud, A. H. M. J.; Vanderspek, R.; Wells, R. D.; Winn, J. N.; Zú...

Abstract

We present the discovery and validation of two TESS exoplanets orbiting nearby M dwarfs: TOI-2084 b, and TOI-4184 b. We characterized the host stars by combining spectra from Shane/Kast and Magellan/FIRE, spectral energy distribution analysis, and stellar evolutionary models. In addition, we used Gemini-South/Zorro & -North/Alopeke high-resolution imaging, archival science images, and statistical validation packages to support the planetary interpretation. We performed a global analysis of multi-colour photometric data from TESS and ground-based facilities in order to derive the stellar and planetary physical parameters for each system. We find that TOI-2084 b and TOI-4184 b are sub-Neptune-sized planets with radii of R-p = 2.47 +/- 0.13R(circle plus) and R-p = 2.43 +/- 0.21 R-circle plus, respectively. TOI-2084 b completes an orbit around its host star every 6.08 days, has an equilibrium temperature of T-eq = 527 +/- 8 K and an irradiation of S-p = 12.8 +/- 0.8 S-circle plus. Its host star is a dwarf of spectral M2.0 +/- 0.5 at a distance of 114 pc with an effective temperature of T-eff = 3550 +/- 50 K, and has a wide, co-moving M8 companion at a projected separation of 1400 au. TOI-4184 b orbits around an M5.0 +/- 0.5 type dwarf star (K-mag = 11.87) each 4.9 days, and has an equilibrium temperature of T-eq = 412 +/- 8 K and an irradiation of S-p = 4.8 +/- 0.4 S-circle plus. TOI-4184 is a metal poor star ([Fe/H] = -0.27 +/- 0.09 dex) at a distance of 69 pc with an effective temperature of T-eff = 3225 +/- 75 K. Both planets are located at the edge of the sub-Jovian desert in the radius-period plane. The combination of the small size and the large infrared brightness of their host stars make these new planets promising targets for future atmospheric exploration with JWST.

Citation

Barkaoui, K., Timmermans, M., Soubkiou, A., Rackham, B. V., Burgasser, A. J., Chouqar, J., …Zúñiga-Fernández, S. (2023). TOI-2084 b and TOI-4184 b: Two new sub-Neptunes around M dwarf stars. Astronomy & Astrophysics, 677, Article A38. https://doi.org/10.1051/0004-6361/202346838

• Journal Article Type: Article
• Acceptance Date: Jun 26, 2023
• Online Publication Date: Aug 30, 2023
• Publication Date: 2023-09
• Deposit Date: Dec 14, 2023
• Journal: Astronomy & Astrophysics
• Print ISSN: 0004-6361
• Electronic ISSN: 1432-0746
• Publisher: EDP Sciences
• Peer Reviewed: Peer Reviewed
• Volume: 677
• Article Number: A38
• DOI: https://doi.org/10.1051/0004-6361/202346838
• Keywords: Space and Planetary Science; Astronomy and Astrophysics